Paraffinic froth treatments are used within the petroleum industry to eliminate aqueous and solid contaminants (i.e., asphaltenes) from the froth to form a clean bitumen product. Paraffinic solvents can be added to reduce viscosity and density of the oil phase, to produce a diluted bitumen product. The diluted bitumen can be transported more effectively and economically through pipelines.
Even though, paraffinic froth treatments are able to clean the bitumen product and reject asphaltene deposits, large asphaltene, and solid aggregates can still form in the bottom of the froth settling units (FSU), which can lead to plugging of equipment and pipelines. Large asphaltene and solid aggregates that are carried over to the tailings solvent recovery system (TSRU) can hinder solvent recovery and cause foaming within the TSRU.
Asphaltenes are defined as the crude oil fraction that is soluble in aromatic solvents and insoluble in low-boiling straight chain alkanes. Asphaltene molecules have complex structures and are typically polar molecules with relatively high molecular weights (approximately 700 to 1,000 g/mole). Asphaltenes can contain carbon, hydrogen, nitrogen, oxygen, and sulfur, as well as trace amounts of vanadium and nickel.
Asphaltenes are typically stable under virgin reservoir conditions, but can be destabilized and precipitate from crude oil during production due to changes in temperature, pressure, chemical composition, and shear rate. Asphaltene deposits can occur throughout the production system, from inside the reservoir formation to pumps, tubing, wellheads, safety valves, flow lines, and surface facilities used in the extraction process. Asphaltene deposits can cause production rate decline and other operational problems, such as increased fluid viscosity and density, and stabilization of oil-water emulsions. The nature of asphaltene deposits, which can appear hard and coal-like or sticky and tar-like, is determined by the composition of the crude oil and the conditions under which precipitation occurred. Asphaltene deposits can block reservoir pores in near-well formations, production tubing, and downstream pipelines.
Therefore, a need exits to develop methods and chemistries for increasing the fluidity of the underflow, decreasing asphaltene formation, and enhancing solvent recovery.